A clinical trial is set up very carefully—participants are selected and excluded, protocols are put in place, and, in many studies, participants and clinicians are blinded. The goal, of course, is to isolate the treatment that is being tested so that it’s positive and negative effects may be measured. With all this planning come various strengths and certain limitations.

He also spoke with MD Magazine® about the strengths and limitations of this study. He highlighted that, unlike many previous trials in this area, the DECLARE-TIMI 58 trial included a large primary prevention population—nearly 60% of participants—which better represents the typical patient with diabetes.

“You certainly see lots of patients with diabetes, but only a portion of those patients have had a heart attack or a stroke previously—many more of them are in this primary prevention group,” said Wiviott.

[Transcript has been edited for clarity.]

What were some strengths of the DECLARE-TIMI 58 trial?

So, I think that probably the major strengths were that this was a large trial—more than 17,000 patients were enrolled in the study. So, it gives us fairly definitive answers, right, we're not concerned that we were underpowered, there was a trend toward this or trend toward that, that we have fairly definitive answers.

I think another strength is the population of patients in this trial is more representative of a population that might be seen in a general practitioner’s office. You certainly see lots of patients with diabetes, but only a portion of those patients have had a heart attack or a stroke previously—many more of them are in this primary prevention group. The population that was enrolled in this trial just had to have one additional risk factor, so, had to have hypertension, had to be a smoker, had to have elevated lipids. So, I think that this is a trial that that reflects the population that people are seeing in clinical practice.

What limitations should be considered when interpreting results?

You know I think that all clinical trials have some limitations and it's not quite the real world, right. We end up having many more interactions with the patients than they do in general clinical practice. So, sometimes the compliance with medications and things like that may be better.

In this trial we also did what's called a run-in period where patients had to take a placebo for a month—they didn't know it was placebo they thought they were taking a study of medication—but if patients didn't comply with that then they weren't enrolled. So, I think that in some senses this is an idealized experiment, right, that more the patients were more likely to take the study medication and were more likely to be compliant. So, you know certainly in order to have benefits you need to be you know on the therapies. I think my biggest limitation for this would be that the compliance was probably better than you might expect in clinical practice.